Mars Was Once Covered In Hip-Deep Flowing Water

The Curiosity rover’s science team has come to a consensus: There was once a large amount of flowing water in Gale Crater. They can’t say when, or for how long, but based on the types, shapes and sizes of rocks they’ve been seeing, they can say, finally, there was flowing water on Mars.

We aren’t talking about a small amount of water either: The stream running from a canyon in Mount Sharpe called Peace Vallis could have been up to hip deep. The water eroded jagged rocks into smooth stones and deposited them in a fan shape across the floor of Gale Crater, Curiosity’s landing site.

The team has examined rock outcroppings from three areas along the rover’s path, all of which indicate that water had eroded rocks into gravel, then deposited them in layers. These layers cemented together forming what’s called a conglomerate rock, similar to a rough cement. 

annotated scour marksCuriosity first spotted these conglomerate rocks at her landing site, Bradbury Landing, where her thrusters blew away a top layer of dust from the surface of the Red Planet. This image has been white balanced to look more like it would on Earth.

Photo: NASA/JPL-Caltech/MSSS

Link outcropping on Mars.The second instance of conglomerate rock is here, at an outcropping named Link. This image was taken Sept. 2, and has been enhanced to show how it would look under Earth lighting conditions.

Photo: NASA/JPL-Caltech/MSSS

Hottah rock outcropping on MarsThe third site, named Hottah, shows a large outcropping of conglomerate rock full of rounded gravel and pebbles. The outcropping was probably wedged out of the crust of Mars when a nearby meteorite hit, but the researchers aren’t sure. Because of the large size of some of the rounded pebbles, the research team determined these rocks were too big to be transported by wind, so they must have been worn away in water.

Photo: NASA/JPL-Caltech/MSSS

The three different sites were all along the trek from Bradbury Landing to Curiosity’s next target Glenelg. The image below shows their locations:

rock outcropping locationsGoulburn, Link and Hottah are all areas where Curiosity has seen rock outcroppings that indicate large amounts of water once flowed over Gale Crater.

Photo: NASA/JPL-Caltech/Univ. of Arizona

The water that deposited these stones likely came from Mount Sharp. The “alluvial fan” of water marks coming from Peace Vallis canyon has been imaged by the Mars HiRise orbiter and the Mars Reconnaissance Orbiter, and was one of the main reasons the Curiosity team landed in Gale Crater.

Peace Vallis, Alluvial Fan and Curiosity's landing site in Gale Crater on MarsHere you can see clearly the canyon the water flowed from, called Peace Vallis, the alluvial fan where the water spread out over the base of the crater, and curiosity’s landing zone marked with a black oval. Where she actually touched down in marked with a +.

Photo: NASA/JPL-Caltech/UofA

“Plenty of papers have been written about channels on Mars with many different hypotheses about the flows in them. This is the first time we’re actually seeing water-transported gravel on Mars. This is a transition from speculation about the size of stream bed material to direct observation of it,” Curiosity science co-investigator William Dietrich of the University of California, Berkeley, said a NASA teleconference.These type of alluvial fans are also seen in California’s Death Valley and several other places on Earth where water flows from mountains into canyons.You can see the similarity between the Mars and Earth sites below:

Mars Link rocks and Earth rocksThis image of conglomerate rock on Mars, at the Link site (on the left) is eerily similar to Earth-bound rock formations (right).

Photo: NASA/JPL-Caltech/MSSS and PSI

“A long-flowing stream can be a habitable environment,” Mars Science Laboratory Project Scientist John Grotzinger, of the California Institute of Technology in Pasadena, said in the teleconference. “It is not our top choice as an environment for preservation of organics, though. We’re still going to Mount Sharp, but this is insurance that we have already found our first potentially habitable environment.”

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